TOP: what has to be done (before decision)

1
TOP what has to be done (before decision)
Toru Iijima / Nagoya (2002.8.31)

• Bar quality seems to be satisfactory.
• Photodetection is (probably) the most critical
  issue.
• TTS
• Chromatic dispersion optimum QE range
• Magnetic field immunity
• Good efficiency effective area ratio
• Position resolution
• Realistic cost, time for development
• High time resolution (pipe-line) read-out
• Background
• Geometry

• cf.) Npe 6 with R5900-U-L16
• at the beam test
• Effective area 40
• Collection eff 50

2
Time Resolution w/ Prototype

• Greatly improved by better polishing accuracy.
• st 85ps (L0.3m), 100ps (L1m), 150ps (L2.3m)
  achieved.

Chromatic dispersion limit (almost)
Single pe resolution, bar quality are almost
understood.
3
Bar TOP Beam Test Result

• Time resolution st(w/o mirror) st(w/ mirror)

4
Application in Belle

• Correlation between qin and TOP, TOF and Npe.
• The most tough part is around qin45.

Separation obtained by
Npe/d25 (dbar thickness in cm)
5
Expected Performance in Belle

• 502K photocathode (green extended bialkari) w/
  QEpeak20

Bar thickness 2cm
Bar thickness 4cm
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Photodetector Comparison
Ceff. Dx st(TTS) B Gain note
1 R5900-U-L16 50 1mm 70-80ps O(106)
2 FM-PMT-L24 85 1mm 100ps 1.0T O(106)
2 FM-PMT-L24 85 1mm 150ps 1.5T O(106)
3 HAPD (gt80) OK 100ps OK O(104)
4 MCP-PMT (60) OK 35ps OK O(106) Life?, Cost?, Size?
5 Si-PM (Geiger mode APD) 30 OK 50ps OK O(106) QE80 (gt500nm), Noise?, size??

• 1,2,3 have been tested
• 4 tests are under way
• 5 B.Dolgoshein (MEPhI, Moscow) et.al., (see
  SLAC-J-ICFA-23)
• Numbers in () are guess, and need be tested or
  confirmed.

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MCP-PMT

• Very good timing performance
• TTS/photon lt 50ps.
• Tests are underway.

R3809-U50 (Hamamatsu) HV-3400V Measured w/ pulse
laser (406nm)
500ps
Single pe peak observable
TDC
s 34ps
After time walk correction
ADC
ADC
TDC
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Single Photon Time Resolution

• 3.5GeV/c _at_ L0.8m, q45
• Bandwidth (Dl)100ns, QE20
• s(t)2 s(TTS)2 s(l)2

Taking longer l ? better resolution (in general),
but dominated with finite TTS.
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If TTS 0

• Taking longer l ?
• Sqrt(Npe) decreases
• DT/s(t) increases faster than decrease of
  sqrt(Npe)
• ?Separation becomes better

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But with finite TTS (L1675ps)

• Taking longer l ?
• DT/s(t) start to saturate (at some point) because
  of TTS
• ?Separation takes the maximum, and then fall with
  sqrt(Npe)

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With the best TTS (MCP35ps)

• Taking longer l ?
• Makes sense (saturation by TTS starts at longer
  l)
• Very good separation !
• 2.3s w/ TTS75ps/l0400nm ?4.3s w/
  TTS35ps/l0600nm

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With TTS50ps (Si-PM)

• The maximum is around 500nm with constant QE20.
• But, if QEe(geom) 35 achieved, it will lift
  up the separation at around 600nm.

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How about narrower bandwidth (50ps)?

• For MCP(TTS35ps), good separation is achieved at
  around 450500nm (green extended bialkarifilter
  ?).
• For Si-PM, it is not good idea.

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Worth for Consideration

• Linear array multianode MCP-PMT w/
• Good packing factor (gt next slide)
• GaAs(P) or Green extended bialkari
• or any photocathode in this range
• Good QE is necessary to compensate the
  geometrical loss in collection eff.
• Reasonable cost
• Si-PM w/
• Good geometrical efficiency
• Low enough noise rate
• Reasonable cost

Questions to HPK !!!
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Flat-Panel MCP-PMT

• Effective area (70-80) (collection eff.)
• Very fast, good timing resolution lt 50ps
• Operate in magnetic field
• A solution complemetary to
• HPD/HAPD (Aerogel-RICH)
• Finemesh PMT (TOP)
• Fundamental (technical) issues
• must be studies before starting
• the test production.
• MCP indium shielding
• MCP mounting etc.
• We start from preliminary investigation for these
  issues.

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Summary

• Photodetection is the present critical issue.
• First, establish L24-g
• Reproduce the result in the paper.
• Assess and solve cross talk problem (if
  significant).
• Packaging to maximize the effective area.
• ? Experimental verification of performance (no
  assumption).
• In parallel, consider/develop alternatives
  sensors
• Expected improvement factor from the above
  achieved point.

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Summary (contd)

• We want to give statements
• The detector will work with such performance
  with the present technology. (no matter how
  good/bad the performance is).
• The performance will be improved by factor of
  with technology under development.
• Indeed, this was the case for the present
  Belle-ACC development.
• Remember Npe (was)
• 1 in early cosmic tests.
• 5 with beams right after I was appointed at
  KEK.
• gt10 approved for construction
• gt15 for the final prototype
• This is the way to improve a new detector !

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Summary (contd)

• High resolution (pipe-line) time read-out
• TS (G.Varner)
• TMC (Y.Arai)
• Connection to other groups (BaBar, ALICE,
  BES-III, )
• Geometry
• Butterfly-TOP
• Easy to analyze, hard to install in Belle
  geometry?
• Bar-TOP
• Easy to install, hard to reconstruct hits.
• Optimization of bar width, thickness etc.
• Background
• Start discussing with Yamamoto-san etc.
• d-ray effects

Geant simulation